This is an application for an R25, Training in Research Diagnosis of Autistic Spectrum Disorders. Autism is a disorder that is defined behaviorally and for which there is neither a clear biological marker nor etiology, although there is strong evidence of genetic contributions. Research has been constrained by the need for reliable and standard diagnostic formulations of these autistic spectrum disorders to ensure comparability of populations. The introduction of two semistructured diagnostic instruments, the Autism Diagnostic Interview-Revised (ADI-R, Lord, Rutter, & LeCouter, 1994) and the Autism Diagnostic Observation Schedule (ADOS, Lord, Rutter, DiLavore, & Risi, 2000), in the 1980's and updated in the 1990's provided this opportunity and has contributed to replicability of findings in neurobiological research since that time. A newer screening questionnaire, the Social and Communication Questionnaire (Berument et al., 1999) has the potential to offer brief screening of potential participants as well. The diagnosis of autism is made complicated by a number of factors, including heterogeneity in IQ and changes in symptoms across development. A "spectrum" of disorders from classical autism to atypical autism, Asperger's Syndrome and Pervasive Developmental Disorder, Not Otherwise Specified (PDD-NOS) that are not reliably distinguished by clinicians all can occur with twin pairs and families. Because the primary features of autism involve social and communication deficits, the contexts in which these behaviors are observed are very important. What the examiner does with the child or adult affects the subject's behavior and the examiner's judgments. Assessments that specify both which aspects of the subject's behavior are scored and what the examiner does (or asks an informant about) provide a compromise between standardized approaches and the need for clinical flexibility in dealing with a population that may range from one extreme to the other in IQ and age. The purpose of this training grant is to provide hands on training in administration and scoring of the instruments for researchers, through annual 2 1/2 day workshops for a total of 30 trainees on each of the two diagnostic instruments and the screening instrument. Follow-up workshops (designed for 30 participants) and a website, with FAQs and a bulletin board (to respond to as many as 50 inquiries a week), and training videotapes (22 in total) will provide mechanisms for maintenance of reliability and support for those learning administration and coding. The addition of training specifically to train other trainers will enable more professionals to train research groups that are requesting training for newly funded or ongoing research projects. [unreadable] [unreadable]